The invention relates to medical patient tables and more particularly to a patient support and positioning system used as part of an X-ray diagnostic medical instrumentation commonly known as a transverse, axial, computerized, tomographic X-ray scanner or "CT" scanner.
The CT scanner is becoming an increasingly popular tool for diagnosis of tumors and the like. Owing to good quality tomographic images with low dosage X-ray radiation without using angiogram techniques and other lengthy, uncomfortable procedures. the CT scanner has been swiftly accepted by the medical profession in brain and abdomical work. CT scanners have a circular opening of approximately 20 inches in which an X-ray beam and opposing scintillator-type detector are translated and rotated according to well-known procedures. An image processor such as the system used in CT scanners sold by Ohio-Nuclear, Inc., Model No. 50. It reconstructs a tomographic or cross-sectional image of the portion of the patient's body in the plane of the scan circle, using in part a construction algorithm.
From the standpoint of patient support, brain scans and abdominal scans are completely different. For the head scan, since only the head need be inserted into the scan circle, the remainder of the body may be supported from one side of the CT scanner apparatus. The abdominal scan presents a more difficult problem in that the patient must be inserted through the scan circle, thus requiring support structure of a different nature. Because of the low dosage radiation and the particular construction algorithms currently in use, non-air parts of the object being scanned should be entirely within the scan circle. Thin high density objects in the scan circle, particularly those with sharp edges, can produce streak artifacts in the image. Thus, it is important that the patient support in the scan circle be as narrow and lightweight as possible. If the table is to have automatic indexing means for taking scans at several axially displaced, adjacent locations, the problems of integrity of the indexing system become apparent: reliable accuracy and safety at a reasonable cost without operator interaction.